Ionic size effect on the radiation‐induced dynamic motion of interstitial halogen in alkali halides

By pulse radiolysis technique, the interaction volume between the dynamic replacement sequence and the H center in RbBr and CsBr has been obtained between liquid nitrogen and room temperatures. Similarly as the previous results on KBr, the temperature dependence of the interaction volume follows an Arrhenius equation, with an activation energy smaller than that for the H center migration in each salt. The activation energies for the interaction volume in RbBr and CsBr and also those in KCl and KBr, previously obtained, are compared with the ionic size of each salt and it is found that the activation energy is smaller in salts with smaller ratio of the halogen‐ion radius to the space between two neighboring alkali ions. The amount of the interaction volume at liquid helium temperature in KI and CsBr is also measured and found to be larger than that in KBr and KCl, which is in accordance with the fact that the ratio of the halogen ion radius to the space between two neighboring halogens is larger in the former salts.